This invention relates to improvements in machines for adhesively attaching a shoe outsole to the bottom of a shoe assembly in an operation known as sole pressing. In a typical sole pressing procedure, an outsole and the bottom of the shoe assembly to which the outsole is going to be attached are precoated with suitable adhesive and the outsole in placed lightly on the bottom of the shoe assembly. The shoe assembly with outsole lightly attached then is placed into a sole press which presses the outsole very firmly against the bottom of the shoe for a length of time to form and maintain the sole against the contour of the shoe assembly while the adhesive sets. The sole pressing machine typically will have a pad, usually in the form of a solid rubber, on which the shoe is placed and against which the shoe and outsole are pressed. The shoe assembly with lightly attached outsole is pressed against the pad, usually by a pair of toe and heel abutments which engage the toe and heel portions of the shoe assembly, press the sole and hold it in a pressed position until the adhesive cures, for example, ten to twenty seconds.
It is very important that the outsole is pressed against the shoe bottom fully and firmly along the complete area where the outsole is to be cemented to the shoe bottom. In addition, the pressure which is applied to the outsole should be sufficient to press the outsole to conform closely to the shape of the shoe bottom. Because of the complex, compound curves characteristic of a typical shoe bottom, some flexibility typically has been necessary in the pad to enable it to conform to the shoe bottom to assure reasonably uniform pressure over the complete surface of the shoe bottom.
Although it would be ideal to have a pad which conforms precisely to the bottom of the shoe assembly being operated on, the ranges of shoe styles, sizes and heel heights make such an ideal impractical. It would be necessary to change pads each time a shoe of a different size was made, or when going from a right shoe to a left shoe, or to a shoe of a slightly different style or a shoe having a different heel height. Because of ever-changing styles as well as the numerous combinations of size, heel height and other characteristics of shoes, it is neither practical nor economical to provide specially fitted pads for each different possible shoe bottom contour.
Over many years, the practice developed to try to utilize a compressible, deformable pad for the shoe bottom which somewhat approximates the general range of shoe bottom contours and configurations which can reasonably be expected to be operated on in the machine. This presented a number of significant problems. When a sole is attached with such a pad, the sole press must be operated to develop a high enough pressing force to make sure that the pad will be deformed and pressed into all regions of the shoe bottom to make sure that all of the variously-contoured outsole surfaces are pressed firmly and adhesively against the bottom of the shoe assembly. The greater the difference in shape between the particular shoe assembly and the contour of the pressing pad, the greater is the pressing force required in order to force the pad fully against all surfaces of the outsole under the minimum pressure required. For example, an effort to use a relatively flat pad configuration (which is normally adapated to operate on shoes having a relatively low heel), with a high-heeled shoe (e.g. "Louis" heels) would require enormous press forces in order to force the pad up into the deep shank area typically found in high heels. The forces required to deform a relatively flat pad into the shank and arch region of a high-heeled configuration often will break the heel or in some instances, can even break or damage the last on which the shoe assembly is held. Also among the common problems encountered when extremely high press forces are required in order to deform a pad is that some portions of the usually fibrous outsole will be so compressed against the bottom of the shoe assembly that normally concealed portions of the shoe assembly will "strike through" and be visible, at least in contour, on the bottom of the shoe assembly. This is sometimes called "X-ray" and results in a poor quality shoe.
As the art of sole pressing developed, improvements were made in pad configurations. For example, U.S. Pat. Nos. 2,568,065 and 2,624,057 to Gulbrandsen, disclose arrangements for adjustable sole press pads which are provided with a pad box to support the pad in a manner which enables the contour defined by the upper surface of the pads to be varied to more or less conform to the particular shoe being worked on. While the devices shown in those patents did expand the range of heel heights which could be operated on, that range still was quite narrow, being restricted to more or less comparatively flat shoes, being unable to operate on a shoe having any significant heel height. In addition, the devices shown in the Gulbrandsen patents required a certain degree of operator skill in that the operator had to pre-set a number of cams to settings best adapted to operate on the particular shoe configuration at hand.
In order to press soles of high-heeled shoes, it became the practice in the art to use pad boxes which received various segments of pads which could be arranged as desired in the pad box to form a pad contour which, in the operator's judgment, would do a proper job on the particular high-heeled shoe at hand. Because of the almost infinite combinations and variations of shoe sizes, styles, and heel heights, the selection of the arrangement of pads was a highly-skilled job in which a highly-skilled operator might be called on to select a group of six to eight pads which could be combined, in the operator's judgment, to provide the best pressing contour for the particular shoe bottom. The parameters in such selection were not limited only to the characteristics of the particular shoe. Rather, there also were considerations concerning the type of last on which the shoe was mounted, the hardness and compressibility of the rubber pad segments, the materials used in the shoe assembly and the like. The operation of a sole press and pad box thus became a highly-skilled portion of the shoe manufacturing process.
U.S. Pat. No. 3,052,901, also to Gulbrandsen, attempted to provide a presser pad and pad box for supporting the pad system which would adjust automatically and more closely to the contour of the bottom of the shoe assembly. To that end, the device in the Gulbrandsen 3,052,901 patent utilized a plurality of vertically-oriented, vertically-shiftable shank pads located in the pad box to engage the deep arch in the shank region of a high-heeled shoe or, conversely, to shift to a more flattened configuration for a flatter shoe. The pad box also included a forepart tray and a heel tray which supported the forepart and heel ends of the shoe respectively. A linkage mechanism connected the forepart tray and heel tray to that part of the pad box which supported the vertically-shiftable shank pads. The device was intended to operate so that in response to an increasing pressing force in each of the heel and toe trays, the linkage would transmit part of that increased force to the support for the shank pads to cause the shank pads to be raised upwardly and firmly into the highly-arched shank region of the high-heeled shoe.
Although the device described in U.S. Pat. No. 3,052,901 is among the more widely used pad box systems for sole pressing, it presents numerous difficulties, perhaps the most serious of which is that it does not operate automatically, as was originally intended, except in a very narrow range of heel heights. This was recognized in a later Gulbrandsen U.S. Pat. No. 3,121,241, which acknowledged that the Gulbrandsen pad box did not operate as intended and that it was still necessary for a highly-skilled operator to rearrange pad elements to fit the particular shoe. The Gulbrandsen '241 patent purported to provide a single, changeable pad which would enable the Gulbrandsen pad box, hopefully to be used with a wide range of heel heights but without the necessity for replacing and rearranging many individual vertically-slideable shank pads.
Notwithstanding the remedial approach suggested by the Gulbrandsen U.S. Pat. No. 3,121,241, it has remained common practice to use the Gulbrandsen pad box but with constant selection and rearrangement of numerous individually, vertically-slideable shank pads to build up a shank pad contour best suited for the particular shoe. It is not uncommon for a sole press operator to have a few hundred pads readily available from which to assemble a proper array for the particular shoe.
The present invention provides improvements in pad box structure and mode of operation which overcome the foregoing difficulties.